Extrusion Process: Comparison Of Types Of Extrusion Process

The extrusion process is broadly divided into four types:

Each of these have different advantages and disadvantages and are therefore more suitable for a variety of different applications. This article takes them individually and brings about a comparison of types of extrusion process in terms of their application specific suitability.

Direct Extrusion
Direct extrusion is the process in which the billet is placed in a heated part of the container and then then it is pushed through the extrusion die using ram pressure. Both the ram and the metal flow in the same direction, and the slides towards the wall of the container helping in a little increase in the pressure necessary to tackle the friction that is created between the billet surface and the container walls. The advantages of the profiles made from the direct extrusion process are: capability to be molded into complex shapes and designs, economical, improved quality ofproducts, clean and smooth. The only disadvantage of the direct extrusion is that it causes creation of frictional forces during the process between the container wall and the billet surface.

Indirect Extrusion
Indirect extrusion on the other hand is just the opposite. The die is placed at the front of the hollow stem for this type of extrusion and then pushed through the container. The billet and the container do not witness any displacement issue and therefore, there is absolute absence of any sort of friction between the two surfaces. It is the absence of friction that results in highly accurate shapes and surface quality in an extruded profile. The advantages of the indirect extrusion process over the direct extrusion process are power economy, better metal flow, uniform section along the length and friction elimination.

Impact Extrusion
The third type of extrusion process that we will be analyzing here is the impact extrusion process. Impact extrusion basically uses a small shot of solid material or a metal slug, placed in the die and then pushed with a high velocity with extreme force and pressure. This process is primarily used for larger sized extruded products that are either stepped or combined shapes. The results of impact extrusion are accuracy precision, tighter tolerance levels, light weight, corrosion resistance, less operation levels, material economy and low costs.

The limitation of this type of extrusion is for profiles that require precise and axially symmetrical cross sections in rotational symmetry. The other issues with impact extrusion are decrease in cross section are, surface residue and probability of very small cracks. Considering these advantages and disadvantages, collapsible tubes and nozzles are the main products of impact extrusion.

Hydrostatic Extrusion
The fourth and the last type of extrusion process to be discussed in this article is the hydrostatic extrusion which is also a form of impact extrusion only. The difference being that instead of a ram, hydrostatic pressure is used to extrude the billet. Billet is subjected to uniform pressure therefore ruling out any type of friction. The advantages of this extrusion process are effective lubrication, good surface finish, dimensional accuracy and minimized deformation possibility.

Tags:- Extrusion Process: Comparison Of Types Of Extrusion Process

Add a comment